CN107459029B - Nitrogen/metal atom doped hollow polyhedral nano carbon shell material and preparation method thereof - Google Patents

Nitrogen/metal atom doped hollow polyhedral nano carbon shell material and preparation method thereof Download PDF

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CN107459029B
CN107459029B CN201710551255.0A CN201710551255A CN107459029B CN 107459029 B CN107459029 B CN 107459029B CN 201710551255 A CN201710551255 A CN 201710551255A CN 107459029 B CN107459029 B CN 107459029B
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nano carbon
carbon shell
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木士春
周煌
何大平
梁启锐
袁帅
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Wuhan University of Technology WUT
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Abstract

The invention relates to a nitrogen/metal atom doped hollow polyhedral nano carbon shell material and a preparation method thereof. The graphene/graphene composite material has a regular hollow polyhedral structure, the particle size is 5-50 nm, few layers of graphene exist, the graphene/graphene composite material has a 2-10 nm mesoporous structure, and the graphene/graphene composite material is particularly distributed in a concentrated mode at 2-4 nm. The electrochemical oxygen reduction performance is excellent, the electrochemical oxygen reduction performance is better than 20% of commercial Pt/C under an alkaline condition, the half-slope potential can reach more than 0.84V vs.

Description

Nitrogen/metal atom doped hollow polyhedral nano carbon shell material and preparation method thereof
Technical Field
The invention relates to a nitrogen/metal atom doped hollow polyhedral nano carbon shell material and a preparation method thereof, belonging to the field of nano material preparation.
Background
Metal-organic framework complexes (MOFs), also called Porous Coordination Polymers (PCPs), generally refer to crystalline materials formed by a self-assembly process of metal ions or metal clusters and organic ligands with a periodic infinite network structure. Because MOFs have different topological structures, different highly ordered pore channel structures, adjustable pore diameters, controllable functional groups, high specific surface area and the like, the MOFs have more applications than the prior porous materials (such as carbon and zeolite molecular sieves). Research over the last decade shows that the metal-organic framework compound has unique physical and chemical properties and potential huge application value in various aspects of magnetism, fluorescence, nonlinear optics, adsorption, separation, catalysis, hydrogen storage and the like. However, despite their excellent structure and potential widespread use, the poor conductivity is a major drawback, limiting wider development. Therefore, further improvements or treatments of MOFs materials are imperative.
In recent years, researchers find that the MOFs materials are calcined and carbonized at high temperature, so that the original morphology of the MOFs can be maintained to a certain extent, and the conductivity of the materials can be greatly improved. For example, Zhang et al in 2014A method for converting a ZIF8 metal organic framework into a nitrogen-doped porous carbon polyhedron through high-temperature calcination (700-1000 ℃) is reported [ Nanoscale,2014,6(12):6590-602.]. Researches show that the original dodecahedron shape of ZIF8 can be well maintained by high-temperature calcination, and the conductivity of the material is effectively improved as organic matter is converted into graphite carbon. For example, Wu et al report 2016 about Zn-Co composite bimetallic organic framework material calcined at high temperaturexCoyBMOF (where x and y represent the molar ratio ZnCo) [ Angewandte Chemie,2016,55(36):10800.]Converted into nitrogen-cobalt doped porous carbon. However, although the MOFs derived carbon material can be obtained through calcination treatment, the morphology of the obtained material is still limited, and the derived carbon material has irregular morphology and sizes of more than 50nm due to certain deformation compared with the original MOFs, and the obtained carbon is amorphous carbon, so that the conductivity of the derived carbon material is influenced. Therefore, the invention provides a novel 5-50 nm regular hollow polyhedral nano carbon shell material derived from MOFs and a preparation method thereof. The material has smaller particle size, more regular morphology and better conductivity than the traditional MOFs derived carbon material, and further expands the application of the MOFs material or the derived material.
Disclosure of Invention
The invention aims to provide a nitrogen/metal atom doped hollow polyhedral nano carbon shell material and a feasible preparation method. The graphene composite material has a regular hollow polyhedral structure and few layers of graphene, the particle size is 5-50 nm, and the graphene composite material has a 2-10 nm mesoporous structure.
In order to achieve the purpose, the invention adopts the technical scheme that:
a nitrogen/metal atom doped hollow polyhedral nano carbon shell has a regular hollow polyhedral structure, the particle size is 5-50 nm, few layers of graphene exist, the shell has a 2-10 nm mesoporous structure, and the shell is particularly distributed in a concentrated mode at 2-4 nm.
According to the scheme, the doping amount of the nitrogen atoms is up to more than 9.0 at%, and the metal doping atoms include but are not limited to Zn, Fe, Co, Cr and the like.
The doping can be single atom doping of Zn, Fe, Co, Cr and the like or multi-atom doping of diatomic or triatomic atoms of ZnCo, ZnFe, FeCo, ZnFeCo and the like.
The preparation method of the nitrogen/metal atom doped hollow polyhedral nano carbon shell specifically comprises the following steps:
2) providing a porous metal organic framework material, wherein the wall thickness of the framework material is not more than 20 nm;
2) putting the powder sample prepared in the step 1) into a high-temperature furnace, keeping inert atmosphere, heating, calcining, carbonizing at high temperature, and naturally cooling;
3) quantitatively placing the powder sample obtained in the step 2) into a solution for stripping treatment to obtain a dispersed nano carbon sheet and nitrogen/metal atom doped nano carbon shell mixed solution;
4) separating the solution obtained in the step 3) to obtain the high-purity nitrogen/metal atom doped nano carbon shell solution.
5) And (4) drying the solution obtained in the step 4) to obtain the nitrogen/metal atom doped hollow polyhedral nano carbon shell material powder.
According to the scheme, the porous metal organic framework material in the step (1) comprises but is not limited to ZnxCoy-BMOF(0<x/y<20)、ZnxFey-BMOF(0<x/y<20)、ZnxCoyFez-TMOF(0<x/(y+z)<20)、ZIF8、ZIF67、MOF5、MOF-100、MIL-53、MIL-100、MIL-101、PCNs。
According to the scheme, the porous metal organic framework material is prepared by adopting a low-temperature (5-15 ℃) hydrothermal method/solvothermal method: under the condition of stirring, quickly (0.1-1 min) dropwise adding a nitrate solution of a metal, particularly a selectable metal, of the metal source compound solution into the organic ligand solution, stirring for 1-6 h at 5-15 ℃, and performing post-treatment to obtain the metal source compound. Compared with the prior art, the method does not need crystallization growth in a hydrothermal high-temperature oven (the temperature in the prior art is more than 120 ℃), strictly controls the low-temperature condition, is favorable for enabling the wall thickness of the formed metal frame material to be within a certain range (not higher than 20nm), and is convenient for later stripping to obtain the nano carbon shell structure. In addition, the solution containing the metal is quickly added into the organic ligand solution such as the dimethyl imidazole within 1min, so that the metal framework material with uniform metal coordination is easier to form, and the uniformly doped metal nano carbon shell is formed at the later stage.
According to the scheme, the high-temperature furnace adopted in the step 2) is a tubular furnace, the inert atmosphere is argon or nitrogen, the high-temperature carbonization temperature is 500-1100 ℃, the heat preservation time is 0.5-8 h, and the heating rate is 2-10 ℃ min-1。
According to the scheme, the solution used in the step 3) is neutral deionized water, a methanol solution with the mass fraction of 10.0-99.5% and preferably 40-99.5%, and an ethanol solution with the mass fraction of 10.0-99.7% and preferably 40-99.7%. Under the same conditions, when a higher-concentration methanol and ethanol organic solvent is selected, the stripping speed is faster than that of a low-concentration or pure water solution (when the mass fraction of the concentration is higher than 80.0%, the stripping speed is 4-8 times that of pure water stripping), and the grain diameter of the hollow polyhedral nano carbon shell obtained by stripping is more uniform (15-25 nm).
According to the scheme, the stripping in the step 3) is ultrasonic stripping, an ultrasonic instrument is a common ultrasonic cleaner or an ultrasonic cell crusher, the ultrasonic power is 5-40 KHz, and the ultrasonic time is 2-100 min (different ultrasonic powers and times are selected for different precursors);
according to the scheme, the separation treatment of the solution in the step 4) is centrifugal separation to obtain an upper layer substance, a separation instrument is a centrifugal machine, the centrifugal time is 1-10 min, and the rotating speed is 500-10000 rpm;
according to the scheme, the drying in the step 5) refers to drying at normal temperature and drying in a common drying oven or a vacuum drying oven.
The above method is applicable to porous metal-organic framework materials, not only to the above listed MOFs materials.
The invention provides a novel preparation method for converting metal-organic frameworks (MOFs) into nitrogen/metal doped nano hollow polyhedral carbon shell material, which mainly selects ZnxCoy-BMOF、ZnxFey-BMOF、ZnxCoyFezMetal organic framework materials of-TMOF, ZIF8, ZIF67, MOF5, MOF-100, MIL-53, MIL-100, MIL-101, PCNs series, etc. by high temperature carbonization, and then by stripping and centrifugingAnd obtaining the nitrogen/metal doped hollow polyhedral nano carbon shell material. The organic metal framework materials are rich in carbon sources, nitrogen sources, zinc sources, cobalt sources, iron sources and the like, and can be directly used as solid heteroatom doping sources. The invention utilizes the characteristics to directly obtain the nitrogen/metal atom doped hollow polyhedral nano carbon shell material by means of high-temperature carbonization, ultrasonic stripping, centrifugal separation and the like on the organic metal framework raw materials. The MOFs is converted into the heteroatom-doped hollow polyhedral carbon nano-shell material, which is firstly proposed and also is firstly obtained by adopting a stripping and centrifuging method.
The invention has the beneficial effects that:
(1) the nano carbon shell material provided by the invention has a regular hollow polyhedral structure, few layers of graphene and a large number of mesopores, the particle size is 5-50 nm, the particle size is far smaller than that of the original MOFs structural material or calcined carbon material (more than 50 nm), the nano carbon shell material has a 2-10 nm mesoporous structure (concentrated at 2-4 nm), ion transmission is facilitated, and the conductivity of the nano carbon shell material is also effectively improved, so that the nano carbon shell material has excellent catalytic properties such as oxygen reduction performance (superior to 20% commercial Pt/C under an alkaline condition, and the half-slope potential can reach more than 0.84V vs. Compared with the traditional MOFs derived carbon material, the carbon material has smaller particle size, more regular morphology and better conductivity; compared with multi-wall fullerene with similar structure, the fullerene has a unique nitrogen/multi-atom doping type structure. Meanwhile, the nano carbon shell material has a large amount of mesopores, and can also be used in the fields of hydrogen storage, energy storage and wave absorption. The characteristic of the few-layer graphene structure also increases the application of MOFs derivative materials in the fields of graphene antenna preparation and the like.
(2) The preparation method of the nitrogen/metal atom doped hollow polyhedral nano carbon shell provided by the invention takes the porous metal organic framework material as the raw material, combines liquid phase stripping, has high efficiency, is simple and easy to implement (simple ultrasonic equipment is adopted, such as an ultrasonic cleaner or an ultrasonic cell crusher or a common centrifuge), and is easy for industrial production. Through the regulation of ultrasonic power and ultrasonic solution, the stripping speed and the particle size of the hollow polyhedral nano carbon shell can be effectively regulated and controlled under the action of ultrasonic shearing force, so that amorphous carbon (namely amorphous carbon dodecahedron with the particle size larger than 50 nm) on the surface of the MOFs-derived carbon material is firstly separated, then the internal porous framework structure is further stripped and decomposed, then an amorphous nano carbon sheet layer is further separated and removed, and finally the uniform nano carbon shell with the regular few-layer graphene and the hollow dodecahedron structure and the particle size smaller than 50nm (even the particle size reaches 5nm) is formed.
Drawings
FIGS. 1a-b are the Metal Organic Frameworks (MOFs) starting materials Zn in example 11.5Co1BMOF Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images.
FIG. 2 is a Transmission Electron Microscope (TEM) image of the cobalt nitrogen-doped carbon polyhedrons obtained in example 1.
FIGS. 3a-c are high power transmission electron microscopy (HR-TEM) images of the nitrogen-cobalt doped hollow polyhedral nanocarbon shell obtained in example 1.
Fig. 4 is a distribution diagram of the pore diameters of the nitrogen-cobalt doped hollow polyhedral nano carbon shell and the nitrogen-cobalt doped carbon polyhedron obtained in example 1.
FIG. 5 is an X-ray photoelectron spectroscopy (XPS) graph of the nitrogen-cobalt doped hollow polyhedral nano carbon shell obtained in example 1.
Fig. 6 is a linear scanning curve (LSV) graph of the nitrogen-cobalt doped hollow polyhedral nanocarbon shells and the nitrogen-cobalt doped carbon polyhedrons obtained in example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
1) Preparation of Zn1.5Co1-BMOF precursor: dimethylimidazole (0.616g) was dissolved in 15ml of methanol, and cobalt nitrate hexahydrate (0.364g) and zinc nitrate hexahydrate (0.558g) were dissolved in 15ml of methanol, and the mixture was stirred at 15 ℃ for 5 minutes, respectively. Then the mixed solution of cobalt nitrate and zinc nitrate is quickly added into the dimethyl imidazole solution for 1min, and stirred for 4h at 15 ℃. 1000Centrifugation was carried out at 0rpm, and the supernatant was replaced with methanol three times. Then the obtained sample is placed in a vacuum drying oven at 70 ℃ and taken out after 12 hours, and Zn can be obtained1.5Co1-a BMOF precursor.
2) Placing the powder sample prepared in the step 1) in a tube furnace, keeping argon atmosphere, heating to 900 ℃, keeping the temperature for 3 hours, and keeping the temperature at the rate of5 ℃ per minute-1Naturally cooling to obtain nitrogen-cobalt doped carbon polyhedron;
3) putting 15mg of the powder sample obtained in the step 2) into 30ml of ethanol solution with the mass fraction of 60% and carrying out ultrasonic treatment in an ultrasonic cleaner for 10KHz for 5min to obtain a dispersed nano carbon sheet and nitrogen-cobalt doped nano carbon shell mixed solution (zinc is volatilized at a high temperature);
4) centrifuging the solution obtained in the step 3) for 5min at 1000rpm of a centrifuge to obtain the high-purity nitrogen-cobalt doped nano carbon shell solution.
5) And (3) placing the sample obtained in the step 4) in a vacuum drying oven at a constant temperature of 70 ℃ (the pressure is 5pa) and drying for 8h to obtain the nitrogen-cobalt doped hollow polyhedral nano carbon shell solid powder.
The content of nitrogen element in the obtained nitrogen-cobalt doped hollow polyhedral nano carbon shell solid powder is 9.39 at.%, and the content of cobalt element is 1.19 at.%.
FIG. 1 shows Zn in example 1 of the present invention1.5Co1BMOF raw material Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images, which are seen to have a regular dodecahedral morphology.
FIG. 2 shows Zn in example 1 of the present invention1.5Co1And a Transmission Electron Microscope (TEM) image of the nitrogen-cobalt-doped carbon polyhedron obtained after the BMOF calcination shows that the dodecahedron morphology of the original MOFs can be still maintained after the calcination.
FIGS. 3a-c are Zn-layers according to example 1 of the present invention1.5Co1-high-power transmission electron microscope (HR-TEM) images of the nitrogen-cobalt-doped carbon polyhedral after BMOF calcination and the nitrogen-cobalt-doped hollow polyhedral nano carbon shell after centrifugal separation treatment, it can be seen that the nano carbon shell structure with a hollow dodecahedron structure and a particle size of-20 nm is obtained after ultrasonic treatment, and there are regular few layers of graphene and obvious lattice fringes.
FIG. 4 shows the nitrogen-cobalt doped hollow polyhedral nano carbon shell (Nanocarbon Cage) obtained in example 1 of the present invention and Zn1.5Co1-Nitrogen-cobalt-doped carbon polyhedra (The carbonised Zn) obtained after BMOF calcination1.5Co1BMOF), both have a large number of aerial structures ranging from 2 to 10nm, whereas the former have more mesopores ranging from 2 to 4 nm.
Fig. 5 is an X-ray photoelectron spectroscopy (XPS) graph of the nitrogen-cobalt doped hollow polyhedral nano carbon shell obtained in example 1 of the present invention, which shows that it mainly contains four elements (C, N, O, Co), wherein the content of nitrogen element is 9.39 at.%, and the content of cobalt element is 1.19 at.%.
FIG. 6 shows the hollow polyhedral carbon nanocapsule (Nanocarbon Cage) doped with nitrogen and cobalt obtained in example 1 of the present invention and Zn1.5Co1-Nitrogen-cobalt-doped carbon polyhedra (The carbonised Zn) obtained after BMOF calcination1.5Co1BMOF), the former half-slope potential reaches 0.84V (vs. rhe) at 0.1M KOH solution, which is 31mV higher than the latter. The former is seen to have higher oxygen reduction activity, better than the latter, and also higher than the 20% commercial Pt/C half slope potential in many reports.
Example 2
1) Preparation of ZIF8 precursor: dimethylimidazole (1.2978g) was dissolved in 40ml of methanol, and zinc nitrate hexahydrate (0.5866g) was dissolved in 40ml of methanol, and the mixture was stirred at 5 ℃ for 5 minutes, respectively. Then the zinc nitrate solution is quickly added into the dimethyl imidazole solution at 0.5min, and stirred for 6h at the temperature of5 ℃. Centrifugation was carried out at 10000rpm, and the supernatant was replaced with methanol three times. And then placing the obtained sample in a vacuum drying oven at 70 ℃ for 12h, and taking out the sample to obtain a ZIF8 precursor.
2) Placing the powder sample prepared in the step 1) in a tubular furnace, keeping nitrogen atmosphere, heating to 900 ℃, keeping the temperature for 3 hours, and keeping the temperature at the rate of5 ℃ per minute-1Naturally cooling to obtain nitrogen-doped carbon polyhedron;
3) putting 10mg of the powder sample obtained in the step 2) into 20ml of ethanol solution with the mass fraction of 80%, and performing ultrasonic treatment in an ultrasonic cleaner for 20KHZ for 8min to obtain dispersed nano carbon sheets and a nitrogen-doped nano carbon shell solution;
4) centrifuging the solution obtained in the step 3) for 6min at 3000rpm of a centrifuge to obtain the high-purity nitrogen-doped hollow polyhedral nano carbon shell solution.
5) And (3) placing the sample obtained in the step 4) in a vacuum drying oven at a constant temperature of 70 ℃ (the pressure is 10pa) and drying for 6h to obtain the nitrogen-doped hollow polyhedral nano carbon shell solid powder.
The content of nitrogen element in the obtained nitrogen-doped hollow polyhedral nano carbon shell solid powder is 12.24 at.%.
Example 3
1) Preparation of Zn1Co1-BMOF precursor: dimethylimidazole (0.616g) was dissolved in 15ml of methanol, and cobalt nitrate hexahydrate (0.546g) and zinc nitrate hexahydrate (0.558g) were dissolved in 15ml of methanol, followed by stirring at 10 ℃ for 5min, respectively. Then the mixed solution of cobalt nitrate and zinc nitrate is quickly added into the dimethyl imidazole solution for 0.5min, and stirred for 4h at the temperature of 10 ℃. Centrifugation was carried out at 10000rpm, and the supernatant was replaced with methanol three times. Then the obtained sample is placed in a vacuum drying oven at 70 ℃ and taken out after 12 hours, and Zn can be obtained1Co1-a BMOF precursor.
2) Placing the powder sample prepared in the step 1) in a tube furnace, keeping argon atmosphere, heating to 1000 ℃, keeping the temperature for 2h, and keeping the temperature at the heating rate of 4 ℃ per minute-1Naturally cooling to obtain nitrogen-cobalt doped carbon polyhedron;
3) putting 15mg of the powder sample obtained in the step 2) into 30ml of methanol solution with the mass fraction of 70% and carrying out ultrasonic cleaning for 10min by using an ultrasonic cleaner at 30KHz, thus obtaining a dispersed nano carbon sheet and nitrogen-cobalt doped nano carbon shell mixed solution;
4) centrifuging the solution obtained in the step 3) for 8min at 2000rpm of a centrifuge to obtain the high-purity nitrogen-cobalt doped nano carbon shell solution.
5) And (4) drying the sample obtained in the step 4) in the air at normal temperature to obtain the nitrogen-cobalt doped hollow polyhedral nano carbon shell solid powder.
The content of nitrogen element in the obtained nitrogen-cobalt doped hollow polyhedral nano carbon shell solid powder is 10.20 at.%, and the content of cobalt element is 1.03 at.%.
Example 4
1) Preparation of ZIF67 precursor: dimethylimidazole (0.616g) was dissolved in 15ml of methanol, and cobalt nitrate hexahydrate (0.546g) was dissolved in 15ml of methanol, followed by stirring at 5 ℃ for 5 minutes, respectively. Then the cobalt nitrate solution is quickly added into the dimethyl imidazole solution at 0.8min, and stirred for 4h at the temperature of5 ℃. Centrifugation was carried out at 10000rpm, and the supernatant was replaced with methanol three times. And then placing the obtained sample in a vacuum drying oven at 70 ℃ for 12h, and taking out the sample to obtain a ZIF67 precursor.
2) Placing the powder sample prepared in the step 1) in a tube furnace, keeping argon atmosphere, heating to 900 ℃, keeping the temperature for 3 hours, and keeping the temperature at the heating rate of 6 ℃ min-1Naturally cooling to obtain nitrogen-cobalt doped carbon polyhedron;
3) putting 10mg of the powder sample obtained in the step 2) into 30ml of ethanol solution with the mass fraction of 60%, and performing 5KHz ultrasonic treatment for 30min by using a cell crusher to obtain a dispersed nano carbon sheet and nitrogen-cobalt doped nano carbon shell mixed solution;
4) centrifuging the solution obtained in the step 3) for 3min at 1000rpm of a centrifuge to obtain the high-purity nitrogen-cobalt doped nano carbon shell solution.
5) And (3) placing the sample obtained in the step 4) in a vacuum drying oven at a constant temperature of 60 ℃ (the pressure is 15pa) and drying for 12h to obtain the nitrogen-cobalt doped hollow polyhedral nano carbon shell solid powder.
The content of nitrogen element in the obtained nitrogen-cobalt doped hollow polyhedral nano carbon shell solid powder is 10.57 at.%, and the content of cobalt element is 6.25 at.%.
Example 5
1) Preparation of Zn2Co1-BMOF precursor: dimethylimidazole (0.616g) was dissolved in 15ml of methanol, and cobalt nitrate hexahydrate (0.273g) and zinc nitrate hexahydrate (0.558g) were dissolved in 15ml of methanol, and the mixture was stirred at 8 ℃ for 5 minutes, respectively. Then the mixed solution of cobalt nitrate and zinc nitrate is quickly added into the dimethyl imidazole solution for 0.2min, and stirred for 4h at the temperature of 8 ℃. Centrifugation was carried out at 10000rpm, and the supernatant was replaced with methanol three times. Then the obtained sample is placed in a vacuum drying oven at 70 ℃ and taken out after 12 hours, and Zn can be obtained2Co1-a BMOF precursor.
2) Placing the powder sample prepared in step 1) in a tubeIn the furnace, nitrogen atmosphere is kept, the temperature is raised to 800 ℃, the temperature is kept for 2h, and the temperature raising rate is 4 ℃ min-1Naturally cooling to obtain nitrogen-zinc-cobalt doped carbon polyhedron;
3) putting 15mg of the powder sample obtained in the step 2) into 30ml of deionized water, and carrying out 40KHz ultrasonic treatment for 80min to obtain a dispersed nano carbon sheet and nitrogen-zinc-cobalt doped nano carbon shell mixed solution;
4) centrifuging the solution obtained in the step 3) for 5min at 6000rpm of a centrifugal machine to obtain the high-purity nitrogen-zinc-cobalt doped nano carbon shell.
5) And (3) placing the sample obtained in the step 4) in a vacuum drying oven at a constant temperature of 60 ℃ (the pressure is 5pa) and drying for 7h to obtain the nitrogen-zinc-cobalt doped hollow polyhedral nano carbon shell solid powder.
The content of nitrogen element in the obtained nitrogen-zinc-cobalt doped hollow polyhedral nano carbon shell solid powder is 9.23 at.%, and the content of zinc element is 3.19 at.%. The content of cobalt element was 1.78 at.%.
Example 6
1) Preparation of MOF5 precursor: terephthalic acid (2.55g, 15mmol) was taken in a 500ml Erlenmeyer flask, 200ml Dimethylformamide (DMF) and triethylamine (8.00g, 80mmol) were added and mixed and stirred at 15 ℃ for 5min, 0.6min a mixture of zinc nitrate hexahydrate (6.08g, 20 mmol) and 10ml Dimethylformamide (DMF) was rapidly dropped and stirred at 15 ℃ for 3 h. Centrifugation was carried out at 10000rpm, and the supernatant was replaced with DMF three times. And then placing the obtained sample in a vacuum drying oven at 70 ℃ for 12h, and taking out to obtain the MOF5 precursor.
2) Placing the powder sample prepared in the step 1) in a tube furnace, keeping argon atmosphere, heating to 1000 ℃, keeping the temperature for 2h, and keeping the temperature at the heating rate of5 ℃ min-1Naturally cooling to obtain nitrogen-doped carbon polyhedron;
3) putting 15mg of the powder sample obtained in the step 2) into 30ml of methanol solution with the mass fraction of 40%, and performing ultrasonic treatment in an ultrasonic cleaner for 10min at 25KHz to obtain a dispersed nano carbon sheet and nitrogen-doped nano carbon shell mixed solution;
4) centrifuging the solution obtained in the step 3) for 6min at 8000rpm of a centrifuge to obtain the high-purity nitrogen-doped nano carbon shell.
5) And (4) drying the sample obtained in the step 4) in the air at normal temperature to obtain the nitrogen-doped hollow polyhedral nano carbon shell solid powder.
The content of nitrogen element in the obtained nitrogen-doped hollow polyhedral nano carbon shell solid powder is 9.80 at.%.
Example 7
1) Preparation of Zn25Co25Fe1-TMOF precursor: dimethylimidazole (0.616g) was dissolved in 15ml of methanol, cobalt nitrate hexahydrate (0.546g) and zinc nitrate hexahydrate (0.558g) were dissolved in 15ml of methanol, and the mixture was stirred at 15 ℃ for 5 min. Then the mixed solution of cobalt nitrate and zinc nitrate is quickly added into the dimethyl imidazole solution for 0.5min, and stirred for 4h at 15 ℃. Centrifugation was carried out at 10000rpm, and the supernatant was replaced with methanol three times. Then the obtained sample is placed in a vacuum drying oven at 70 ℃ and taken out after 12 hours, and Zn can be obtained1Co1-a BMOF precursor. The obtained Zn is1Co1-BMOF was dissolved in 15ml methanol, 15ml ferric nitrate nonahydrate solution (0.030g ferric nitrate nonahydrate dissolved in 15ml methanol) was added under stirring at 35 ℃ and further stirred for 4 h. Centrifugation was carried out at 10000rpm, and the supernatant was replaced with methanol three times. Then the obtained sample is placed in a vacuum drying oven at 70 ℃ and taken out after 12 hours, and Zn can be obtained25Co25Fe1-a TMOF precursor.
2) Placing the powder sample prepared in the step 1) in a tubular furnace, keeping nitrogen atmosphere, heating to 1000 ℃, keeping the temperature for 2h, and keeping the temperature at the heating rate of 6 ℃ min-1Naturally cooling to obtain nitrogen-cobalt-iron doped carbon polyhedron;
3) putting 15mg of the powder sample obtained in the step 2) into 30ml of ethanol solution with the mass fraction of 90%, and performing ultrasonic treatment for 40min by using an ultrasonic cell crusher at 10KHz to obtain dispersed nano carbon sheet and nitrogen-cobalt-iron doped nano carbon shell mixed solution;
4) centrifuging the solution obtained in the step 3) for 2min at 10000rpm of a centrifugal machine to obtain the high-purity nitrogen-cobalt-iron-doped nano carbon shell.
5) And (4) drying the sample obtained in the step 4) in the air at normal temperature to obtain the nitrogen-cobalt-iron doped hollow polyhedral nano carbon shell solid powder.
The content of nitrogen element, cobalt element and iron element in the obtained nitrogen-cobalt doped hollow polyhedral nano carbon shell solid powder is 10.10 at.%, 1.03 at.% and 0.79 at.%, respectively.
Example 8
1) Preparation of Zn1Co1.5-BMOF precursor: dimethylimidazole (0.616g) was dissolved in 15ml of methanol, and cobalt nitrate hexahydrate (0.546g) and zinc nitrate hexahydrate (0.372g) were dissolved in 15ml of methanol, followed by stirring at 10 ℃ for 5 minutes, respectively. Then the mixed solution of cobalt nitrate and zinc nitrate is quickly added into the dimethyl imidazole solution for 1min, and stirred for 4h at the temperature of 10 ℃. Centrifugation was carried out at 10000rpm, and the supernatant was replaced with methanol three times. Then the obtained sample is placed in a vacuum drying oven at 70 ℃ and taken out after 12 hours, and Zn can be obtained1Co1.5-a BMOF precursor.
2) Placing the powder sample prepared in the step 1) in a tube furnace, keeping argon atmosphere, heating to 900 ℃, keeping the temperature for 3 hours, and keeping the temperature at the rate of5 ℃ per minute-1Naturally cooling to obtain nitrogen-cobalt doped carbon polyhedron;
3) putting 15mg of the powder sample obtained in the step 2) into 30ml of ethanol solution with the mass fraction of 99.7 percent, and performing 5KHz ultrasonic treatment on the powder sample for 5min by using an ultrasonic cell crusher to obtain dispersed nano carbon sheet and nitrogen cobalt doped nano carbon shell mixed solution;
4) centrifuging the solution obtained in the step 3) for 10min at 500rpm of a centrifuge to obtain the high-purity nitrogen-cobalt doped nano carbon shell.
5) And (3) placing the sample obtained in the step 4) in a vacuum drying oven at a constant temperature of 70 ℃ (the pressure is 5pa) and drying for 8h to obtain the nitrogen-cobalt doped hollow polyhedral nano carbon shell solid powder.
The content of nitrogen element in the obtained nitrogen-cobalt doped hollow polyhedral nano carbon shell solid powder is 9.15 at.%, and the content of cobalt element is 3.66 at.%.
Example 9
1) Preparation of Zn25Fe1-BMOF precursor: dimethylimidazole (1.2978g) was dissolved in 40ml of methanol, and zinc nitrate hexahydrate (0.586g) was dissolved in 40ml of methanol, and the mixture was stirred at 5 ℃ for 5 minutes, respectively. Then adding the zinc nitrate solution into the dimethyl imidazole solution quickly for 1min, and stirring for 6h at the temperature of5 DEG C. Centrifugation was carried out at 10000rpm, and the supernatant was replaced with methanol three times. And then placing the obtained sample in a vacuum drying oven at 70 ℃ for 12h, and taking out the sample to obtain a ZIF8 precursor. The resulting ZIF8 was dissolved in 15ml of methanol, 15ml of ferric nitrate nonahydrate solution (0.030g of ferric nitrate nonahydrate dissolved in 15ml of methanol) was quickly added under stirring at 5 ℃ for 1min, and further stirred for 4 h. Centrifugation was carried out at 10000rpm, and the supernatant was replaced with methanol three times. Then the obtained sample is placed in a vacuum drying oven at 70 ℃ and taken out after 12 hours, and Zn can be obtained25Fe1-a BMOF precursor.
2) Placing the powder sample prepared in the step 1) in a tube furnace, keeping nitrogen atmosphere, heating to 800 ℃, keeping the temperature for 3h, and keeping the temperature at the heating rate of5 ℃ min-1Naturally cooling to obtain the nitrogen-iron atom doped carbon polyhedron;
3) putting 10mg of the powder sample obtained in the step 2) into 20ml of ethanol solution with the mass fraction of 80%, and performing ultrasonic cleaning in an ultrasonic cleaner for 10KHz for 60min to obtain a dispersed nano carbon sheet and nitrogen-iron doped nano carbon shell mixed solution;
4) centrifuging the solution obtained in the step 3) for 8min at 5000rpm of a centrifuge to obtain the high-purity nitrogen-iron doped nano carbon shell.
5) And (3) placing the sample obtained in the step 4) in a vacuum drying oven at a constant temperature of 50 ℃ (the pressure is 10pa) and drying for 6h to obtain the ferronitrogen doped hollow polyhedral nano carbon shell solid powder.
The content of nitrogen element in the obtained solid powder of the nitrogen-iron doped hollow polyhedral nano carbon shell is 10.24 at.%, and the content of iron element is 1.23 at.%.
Example 10
1) Preparing an MIL-101 precursor: 3g of chromium nitrate nonahydrate and 0.82g of terephthalic acid are weighed and respectively put into 10ml of deionized water, stirred for 5min at 10 ℃, and then the chromium nitrate nonahydrate and the terephthalic acid are quickly added into the deionized water within 0.5min, then 0.2g of hydrofluoric acid with the mass fraction of 40% is added, stirred for 6h at 15 ℃, centrifuged at 10000rpm, and supernatant is replaced by the deionized water for three times. And then placing the obtained sample in a vacuum drying oven at 70 ℃ for 12h, and taking out to obtain the MIL-101 precursor.
2) Placing the powder sample prepared in the step 1) in a tube furnace, keeping argon atmosphere,heating to 900 deg.C, maintaining for 6h at a heating rate of 6 deg.C/min-1Naturally cooling to obtain nitrogen-chromium doped carbon polyhedron;
3) putting 15mg of the powder sample obtained in the step 2) into 30ml of methanol solution with the mass fraction of 99.5% and performing ultrasonic cleaning with an ultrasonic cleaner for 10KHz for 10min to obtain dispersed nano carbon sheets and a nitrogen-chromium doped nano carbon shell solution;
4) and (3) centrifuging the solution obtained in the step 3) for 3min at 6000rpm of a centrifugal machine to obtain the high-purity nitrogen-chromium doped nano carbon shell.
5) And (3) drying the sample obtained in the step 4) in a common drying oven at 70 ℃ to obtain the nitrogen-chromium doped hollow polyhedral nano carbon shell solid powder.
The content of nitrogen element in the obtained nitrogen-chromium doped hollow polyhedral nano carbon shell solid powder is 9.60 at.%, and the content of chromium element is 2.09 at.%.

Claims (10)

1. A nitrogen/metal atom doped hollow polyhedral nano carbon shell material is characterized in that: the graphene is doped with nitrogen or co-doped with nitrogen and metal atoms, has a regular hollow polyhedral structure, has a particle size of 5-50 nm, contains few layers of graphene, and has a 2-10 nm mesoporous structure.
2. The nitrogen/metal atom doped hollow polyhedral nanocarbon shell material according to claim 1, wherein: the doping amount of the nitrogen atoms is up to more than 9.0at percent; the metal doping atoms are selected from one or more of Zn, Fe, Co and Cr, and are doped by single atoms of Zn, Fe, Co or Cr, or by double atoms of ZnCo, ZnFe and FeCo, or by three atoms of ZnFeCo.
3. The method for preparing the nitrogen/metal atom doped hollow polyhedral nano carbon shell material according to claim 1, which is characterized in that: the method specifically comprises the following steps:
1) providing a porous metal organic framework material, wherein the wall thickness of the framework material is not more than 20 nm;
2) putting the powder sample prepared in the step 1) into a high-temperature furnace, keeping inert atmosphere, heating, calcining, carbonizing at high temperature, and naturally cooling;
3) quantitatively placing the powder sample obtained in the step 2) into a solution for stripping treatment to obtain a dispersed nano carbon sheet and nitrogen/metal atom doped nano carbon shell mixed solution;
4) separating the solution obtained in the step 3) to obtain a high-purity nitrogen/metal atom doped nano carbon shell solution;
5) and (4) drying the solution obtained in the step 4) to obtain the nitrogen/metal atom doped hollow polyhedral nano carbon shell material powder.
4. The method for preparing the nitrogen/metal atom doped hollow polyhedral nano carbon shell material according to claim 3, which is characterized in that: the porous metal organic framework material in the step (1) is selected from ZnxCoyBMOF, where 0<x/y<20；ZnxFeyBMOF, where 0<x/y<20；ZnxCoyFez-TMOF, where 0<x/(y+z)<20; ZIF 8; ZIF 67; MOF 5; MOF-100; MIL-53; MIL-100; MIL-101 or PCNs.
5. The method for preparing the nitrogen/metal atom doped hollow polyhedral nano carbon shell material according to claim 3, which is characterized in that: the porous metal organic framework material is prepared by adopting a low-temperature solvothermal method at 5-15 ℃: under the condition of stirring, the metal source compound solution is quickly dripped into the organic ligand solution within 0.1-1 min, and is stirred for 1-6 h at the temperature of 5-15 ℃ for post-treatment to obtain the metal source compound.
6. The method for preparing the nitrogen/metal atom doped hollow polyhedral nano carbon shell material according to claim 3, which is characterized in that: the high-temperature furnace adopted in the step 2) is a tubular furnace, the inert atmosphere is argon or nitrogen, the high-temperature carbonization temperature is 500-1100 ℃, the heat preservation time is 0.5-8 h, and the heating rate is 2-10 ℃ min-1。
7. The method for preparing the nitrogen/metal atom doped hollow polyhedral nano carbon shell material according to claim 3, which is characterized in that: the solution used in the step 3) is neutral deionized water, a methanol solution with the mass fraction of 10.0-99.5% or an ethanol solution with the mass fraction of 10.0-99.7%.
8. The method for preparing the nitrogen/metal atom doped hollow polyhedral nano carbon shell material according to claim 3, which is characterized in that: the solution used in the step 3) is 40-99.5% methanol solution or 40-99.7% ethanol solution.
9. The method for preparing the nitrogen/metal atom doped hollow polyhedral nano carbon shell material according to claim 3, which is characterized in that: and 3) stripping in the step 3) is ultrasonic stripping, an ultrasonic instrument is a common ultrasonic cleaner or an ultrasonic cell crusher, the ultrasonic power is 5-40 KHz, and the ultrasonic time is 2-100 min.
10. The method for preparing the nitrogen/metal atom doped hollow polyhedral nano carbon shell material according to claim 3, which is characterized in that: the separation treatment of the solution in the step 4) is centrifugal separation to obtain an upper layer substance, the separation instrument is a centrifugal machine, the centrifugal time is 1-10 min, and the rotating speed is 500-10000 rpm.
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